Submitted by: Jeremy Nelson PT
Component 3.0 Sitting with Back Unsupported But Feet Supported
In the seated position, the center of gravity is closer to the base of support. The base of support is also wider than what we saw in the unsupported symmetrical standing of the previous element. As a result, it is a less complex position to maintain and work in and has a lower kinetic energy. It could then seem that this component, being easier would require less attention then more demanding postures.
This is not true, and in fact sitting capacity will be important information when working on higher levels of function. The chestnut that you must first stand before you can sit makes sense. And how one sits will influence the capacity to stand as was discussed in the first component. Although not part of the test scoring, the clinician may investigate the capacity to anterior weight shift and explore the patient’s capacity to control dynamic motion. The seated position can be an entry point into improving squat transitions and standing activity.
Within the Berg, this component time is also being measured in time. This data point is often interpreted as level of strength and endurance in the extensors must musculature. More specifically it is a measure of the efficiency of maintaining the COG over the BOS in this position. As was described in the unsupported standing, a postural assessment is helpful to examine the passive range of motions and muscle lengths to attain this position. Most important is the pelvic positioning. This will have a dominant influence on the spinal posture and further positions the COG behind the BOS when in a posterior tilt. LE posturing into excess adduction will decrease the control of the COG over the BOS and instead lead to posterior rotation moment that leads to the patient using a forward head posture strategy. In essence the patient may be trying to pull herself forward with the anterior chain resulting in poor efficiencies, likely leading to fatigue and hyperactivity of pecs, iliospoas, adductors, kyphosis and poor diaphragmatic excursion. What may at first be a lack of extensors control is more likely excess activation of the anterior chain with reciprocal inhibition of the posterior chain in sitting.
A principal in using structured motion is to always have a place to go. When the client is unable to complete a certain activity in a position, step one level down within the BOS key, or into a new BOS. For this example the difficulty is going from sitting to standing. We discussed this squat pattern based movement before. Before we began working on the critical tasks needed to accomplish the goal of standing up, the supporting critical tasks within sitting had to be completed. Within this context the choice of intervention would be to enhance the patient’s ability to complete the critical task. Within a problem solving structure the approach would be to work on leg strength to promote better sit to stand.
The critical task is a derivative of the two components of COG and BOS. Each part must do its part to support the change in COG within the changing BOS. Consider the following scenario as an exploration of therapeutic exercise as an intensification of the critical task. Establishing the base of support is the first place to start in the seated position. The seated position BOS includes the lower extremities and pelvis. Begin by positioning the feet shoulder width apart and knees and into a flexed position at approximately hundred degrees of flexion and the ankles at neutral to 5° dorsiflexion. Hip abduction to roughly 35° promotes the pelvis rotated to neutral to weight bearing on the ischial tuberosities.
A possible cause of a patient needing moderate or maximal assist is that the knees are too close together. This limits the anterior weight shift capacity as they bend forward the femur stops the anterior rotation of the pelvis. As a result the lumbar spine flexion occurs and this actually positions the core into an area of flexion instead of an area neutral extension which is the body position required to attain control of the COG. In addition it positions a center of gravity behind the base of support so it’s very important that the knees are apart from each other and that the person can spill forward in that open space between the knees. Teaching the hip hinge using the physio ball initiates the core stability that supports the hip joint do the movement. Without the core stability established lumbar spine flexion occurs and causing extension of the hip joint in the closed chain.